There are presently available a number of motor control circuits for controlling the speed of a disc mounted on a spindle motor in a disc drive. One such motor control circuits can be found in European Publication No. 0 251 785, listing Squires et al. as the inventor. This disclosure teaches a process for a achieving and maintaining operating speed for the spindle motor. As part of this process, commutation is accomplished using signals generated from the spindle motor itself.
In some prior art tape drives, motor commutation is accomplished based on signals embedded on the tape itself.
With respect to the above-indicated disc drives and tape drives, there is a positive direct relationship between the media, be it the disc or the tape, and the spindle motor which drives the media.